To date, illuminating devices formed by combining a fluorescent member and a semiconductor light-emitting element, such as a light-emitting diode element or a semiconductor laser device, that emits light used as an excitation light have been known. Light-emitting diode elements or semiconductor laser devices used as excitation light sources often include a nitride semiconductor that emits light in a spectrum ranging from ultraviolet to blue. Thus, a material that can convert light in the corresponding wave range to green to red light is selected as a fluorescent member. Consequently, an illuminating device that emits light of a desired color can be formed. Such an illuminating device is disclosed in, for example, PTL 1.
Here, when the intensity of light emitted from the semiconductor light-emitting elements reaches or exceeds a specific intensity, such light becomes hazardous to the human body. Particularly, since laser beams emitted from semiconductor laser devices are coherent light, when directly impinging on the human eye, laser beams have an extremely high power density and thus are highly likely to damage eyes.
On the other hand, even if the above-described illuminating devices include semiconductor laser devices as light sources, laser beams can be safely directed at the human eye as long as they are emitted to fluorescent members because laser beams scattered by the fluorescent members are no longer coherent light. Thus, some have proposed using semiconductor laser devices as light sources (excitation light sources) instead of existing light sources such as incandescent light bulbs.
For example, PTL 2 describes an electronic endoscope device including a semiconductor laser as a light source of illumination light that illuminates an object in a lumen. This electronic endoscope device includes an endoscope insertable portion and a device body connected to the endoscope insertable portion. On the device body, a semiconductor laser device (laser chip) is mounted as a light source. Laser beams oscillated by the semiconductor laser device are transmitted through a communication fiber installed in the endoscope insertable portion and emitted to a fluorescent filter (fluorescent member) disposed at the tip of the endoscope insertable portion. The fluorescent filter emits white light when irradiated with laser beams, whereby the object is illuminated. In addition, an imaging unit including an image sensor is disposed at the tip of the endoscope insertable portion. This imaging unit is driven by a signal processor installed in the device body and imaging signals from the imaging unit are signal-processed so that an endoscopic image is displayed on a monitor.
When such an electronic endoscope device has received damage, such as breakage of the communication fiber, laser beams may leak out of the endoscope insertable portion. In view of this, PTL 2 discloses an illumination system in which laser beams do not leak out of an endoscope insertable portion even in the case of occurrence of damage. Specifically, the system electrically senses breakage or a short circuit of a cable that connects a signal processor and an imaging unit. When the system detects breakage or a short circuit of the cable, the system controls laser beam output such that laser beams do not leak out of the endoscope insertable portion.
In addition, PTL 3 discloses an illuminating device that includes a reflected-light detecting unit that detects a specific wavelength of light reflected off a fluorescent member for improvement of eye safety.